What's the actual use of 'fail' in JUnit test case?

Question

What\'s the actual use of \'fail\' in JUnit test case?

Answer 1

In concurrent and/or asynchronous settings, you may want to verify that certain methods (e.g. delegates, event listeners, response handlers, you name it) are not called. Mocking frameworks aside, you can call fail() in those methods to fail the tests. Expired timeouts are another natural failure condition in such scenarios.

For example:

final CountDownLatch latch = new CountDownLatch(1);

service.asyncCall(someParameter, new ResponseHandler() {
    @Override
    public void onSuccess(SomeType result) {
        assertNotNull(result);
        // Further test assertions on the result
        latch.countDown();
    }

    @Override
    public void onError(Exception e) {
        fail(exception.getMessage());
        latch.countDown();
    }
});

if ( !latch.await(5, TimeUnit.SECONDS) ) {
    fail("No response after 5s");
}